As part of an investigation through a local TV station and North Caroline State University, more than 100 lunchboxes were tested for various forms of bacteria by graduate students, the article stated.

According to the article, half of the lunchboxes tested were positive for low levels of Staphylococcus, while three percent tested positive for Listeria.

Leeann Jaykus, a professor of food, bioprocessing and nutrition science at N.C. State who oversaw the test, said the biggest surprise – and a legitimate health concern — was that more than a dozen lunchboxes tested had fecal coliform, the article noted.

The study points to improper handwashing as the likely source for the fecal contamination, the article added.